SOURCES AND FLUX OF NUTRIENTS IN THE MISSISSIPPI RIVER BASIN: MONITORING, MODELING, & RESEARCH NEEDS Donald A. Goolsby, U.S. Geological Survey

 Monitoring  Modeling  Research

HISTORICAL NASQAN AND HYDROLOGIC BENCHMARK STATIONS Source: Alexander, R.B., and others, 1997, USGS Fact Sheet FS NASQAN STATIONS ACTIVE IN 2002

Long-term trends in nitrate concentrations and flux

42 Interior Basins used in for source/yield estimates in CENR Assessment

CURRENT STATUS (2002) OF NUTRIENT MONITORING IN 42 BASINS IN THE MISSISSIPPI RIVER BASIN

 Establish a nutrient monitoring program in the MARB to determine the effects of voluntary actions, changes in nutrient management practices, and new policies aimed at reducing the nutrient flux to the Gulf of Mexico.  Reestablish nutrient monitoring in some of the 42 interior basins used in the CENR assessment. These sites have the benefit of a long period of historical data.  Augment monitoring at this scale by nutrient monitoring in selected small basins, where the effects of changes in nutrient inputs will be most noticeable.  Any monitoring program that is established must include a plan for storage, compilation, timely synthesis and dissemination of data, and periodic reporting of results to all interested parties. MONITORING NEEDS

Prepared by R. P. Hooper, USGS USGS (WATER) NUTRIENT MONITORING IN FISCAL YEAR 2001

ATMOSPHERIC DEPOSITION NADP NITRATE DEPOSITION DATA NITRATE DEPOSITION BY BASIN

LANDUSE, NITROGEN INPUTS AND OUTPUTS

MONITORING NEEDS CONT.  Continued collection of agricultural statistics like those provided by USDA/NASS  Continued monitoring of nitrogen atmospheric wet deposition (NADP)  Expand efforts to monitor nitrogen (including organic nitrogen) in dry deposition  Establish an effluent monitoring program to improve estimates of nutrient inputs from municipal and industrial sources.

 Monitoring  Modeling  Research

OBSERVED AND PREDICTED NITRATE FLUX TO THE GULF OF MEXICO N flux = 0.049Fert Q Resid 1

MODEL: N LM = 0.26*W 0.94 *e (0.17*NANI *NANI6-9)) Source: McIsaac, G.F., David, M.B., Gertner, G.Z., and Goolsby, D.A., 2001, Nitrate Flux in the Mississippi River: Nature, v. 14, p OBSERVED AND ESTIMATED NITRATE FLUX IN LOWER MISSISSIPPI RIVER

Nitrogen yields of 42 basins (A), nitrogen inputs during 1992 (B), and average annual nitrogen yields of streams for (C ) (kg/km 2 /yr – kilograms per square kilometer per year modified from Goolsby and others, 1999 Total N yield (kg/km 2 /yr) = (pctcrop 2 ) (popden) (no3dep)

2002 Area = Theb May-Q May NO3_conc Theb MayQ-1

MODELING NEEDS  Improve statistical models to provide better estimates of flux at various time scales, sources, trends, etc.)  Watershed and agricultural models to link processes, agricultural practices, hydrology, etc. with nitrogen losses to ground water and streams.  Models to provide feed back for improved design of monitoring programs.

 Monitoring  Modeling  Research

NITROGEN MASS BALANCE FOR MISSISSIPPI RIVER BASIN Source: Goolsby and others, 1999, CENR Topic 3 report, figure 6.7

RESEARCH NEEDS  Better understanding of nitrogen dynamics in soils: mineralization, immobilization, leaching, storage, etc.  Research in small watersheds, with and without tile drainage to better understand dynamics and transport of water and nitrogen from fields to streams.  Examine importance of instream processes, such as denitrification in removing nitrogen from streams: effect of stream size and characteristics.  Develop a nitrogen mass balance (inputs and outputs) for the Mississippi basin  Provide feedback for modeling and monitoring efforts  Share results of research, modeling, and monitoring via periodic technical symposia.

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